The present invention relates to an organometallic complex, and more specifically to an organometallic complex used in an organic light-emitting diode.
Organic electroluminescent devices are popular in flat panel display due to their high illumination, light weight, self-illumination, low power consumption, simple fabrication, rapid response time, wide viewing angle, and no backlight requirement.
When an external electric field is applied to an organic electroluminescent device, electrons and holes are injected from cathode and anode, respectively, and then recombined to form excitons. Energy is further transported from excitons to luminescent molecules with continuous application of an electric field. Finally, luminescent molecules emit light converted from energy. A common organic electroluminescent device structure comprises an ITO anode, a hole transport layer, an emitting layer, a hole blocking layer, an electron transport layer, and a cathode. A complex organic electroluminescent device, however, may further comprise a hole injection layer disposed between an anode and a hole transport layer or an electron injection layer disposed between a cathode and an electron transport layer to improve injection efficiency of carriers, reducing driving voltage or increasing recombination thereof.
With development of synthesis techniques, various synthetic organic compounds for use in organic electroluminescent devices have been provided. Such luminescent materials are fluorescent and phosphorescent materials. Generally, phosphorescent materials are composed of transition metal complexes. Due to heavy atom effect, electrons of a phosphorescent material may span multiple energy levels to form a triplet excited state, resulting in increased phosphorescence emission, simultaneously reducing fluorescent intensity. Thus, phosphorescent materials exhibit three times the luminescence of fluorescents. Consequently, development of a phosphorescent material with high luminescent efficiency is a critical factor in improvement of luminescent performance of organic electroluminescent devices.